Global warming can be kept to below 1.5 °C above pre-industrial temperatures without using Bioenergy with Carbon Capture and Storage (BECCS), or at least not much. So says a study in Nature Climate Change. Whereas the IPCC, IEA and others have suggested that negative emission technologies like BECCS would be vital, the new paper claims that a range of ambitious mitigation options can minimize or, collectively, eliminate the need for BECCS.

The study, by researchers at the PBL Netherlands Environmental Assessment Agency, and the Copernicus Institute for Sustainable Development at Utrecht University, looks to the much more rapid adoption of renewables and energy efficiency, more emphasis on non-carbon greenhouse gas reduction, and also to lifestyle changes, including less car use and less meat-eating. That may be hard, but so would BECCS – vast land areas of biomass would be needed to have a significant impact, and that anyway assumes CCS can be done at scale. The paper says “existing studies hardly look into more aggressive implementation of options, such as rapid implementation of the best available technologies or deep reduction of non-CO₂ GHGs [greenhouse gases]. Technology development could also be more rapid than typically assumed”.

So it may be possible to limit or avoid BECCS. Not so, says Bert Metz, former co-chair of the Intergovernmental Panel on Climate Change (IPCC) working group on mitigation and now senior adviser to the European Climate Foundation. He told Carbon Brief: “It is highly unlikely that the investigated options can indeed all be applied simultaneously to the extent assumed in the paper and that the full impacts of each of the options can be delivered in practice, as the assumptions are very ambitious.”

It may come down to faith in technology and change

Dave Elliott

However, Stephan Singer, senior adviser on global energy policies to the NGO umbrella group Climate Action Network, told Carbon Brief: “Lifestyle changes for the globally high-consuming and emitting rich…are [a] fundamental part of the equation…This is not limited to individual dietary changes…[it] also includes significant transport and travel behavioural change, institutionalized longer durability of products, higher reusability of components, new materials and, overall, a circular economy.” Indeed, as Carbon Brief noted, some would go further and look to a world without relentless economic growth. But for now, what seems to have happened is that BECCS has been dethroned as a default “backstop”. Detlef van Vuuren, senior researcher at PBL and lead author of the new report, told Carbon Brief that it was “unfortunate” that work to date on meeting 1.5 °C has been so dominated by BECCS.

Wider debate

You could say the same for CCS generally. The BECCS debate is, after all, a subset of the wider debate about CCS. As I have reported in previous posts, although the IPCC, IEA and most oil companies are keen on fossil CCS, and it plays a major role in most of their long-term energy scenarios, the reality is that, with some exceptions, it is pretty much stalled, with just two fossil CCS projects in North America. That isn’t surprising. In the absence of serious carbon emission taxes, there is no real incentive for CCS – and it’s costly. There is some interest in CCU – utilization of captured fossil-sourced carbon dioxide for making synfuels, since they have value. But when they are burnt they generate carbon dioxide again. So we are no further forward. Certainly, in the UK, the latest scenario from the UK government Department for Business, Energy and Industrial Strategy (BEIS) has hardly any CCS/CCU, even by 2035.  ­

However, bucking that trend, a new wider report published by the Royal Society says that what it labels as Carbon Dioxide Removal (CDR) is still vital to meet the 1.5 °C Paris target without overshoot. As I noted above, the PBL BECCS paper criticized existing studies for not looking at the alternative options enough, but this new wider study, by researchers from Germany’s Potsdam Institute and others (including, interestingly, from PBL and the Copernicus Institute), has now tried to do that, at least in part.

Exploring a range of system models, the report concludes that they will be not be sufficient – we will need CDR in nearly every case. It says that “for a 1.5 °C CO₂ budget up to 550 Gt CO₂, overshoot will be inevitable; CDR will be required to return to the 1.5 °C limit if the limiting cases formulated in our analysis hold. For budgets between 550 and 650 Gt CO₂, we find CDR trajectories that allow to stay below 1.5 °C without overshoot in the steepest fossil fuel and industry-related CO₂ emissions reduction cases. For budgets of 650 Gt CO₂ and higher, the steepest emissions reduction cases are sufficient to limit warming to 1.5 °C without CDR deployment”.

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Whatever happened to carbon capture?

What’s more, it says “these steepest cases are based on limiting cases for carbon intensity improvements of electricity and non-electric energy supply, electrification of energy end-use, final energy demand reductions, and CDR deployment. They are designed to describe outer bounds beyond which developments are very unlikely. But they themselves may also be unlikely to attain, with the exception of power sector decarbonization”.

Although there are sectorial exceptions, overall, the “below 1.5 °C” target can’t be attained without CDR. Even staying under 2 °C would be hard. But that’s essentially because of the continued use of fossil fuels. It is true that it would be very hard to phase all of them out rapidly: we are struggling with coal, while resistance to oil use is patchy and gas use is still booming. Renewables too are booming, but not fast enough to squeeze the fossil fuels – and also nuclear – out quickly. A much more rapid expansion of renewables and efficiency would help – as proposed in the first study, along with other measures aimed at taming energy demand. But the numbers in the second study say that’s still not enough.

Choice of views

Which view to believe?  The modelling, which seems to be saying we must continue with fossil fuels, and so with CDR? Or approaches looking to more creative strategies but wary of technical fixes like CDR, and BECCS in particular? And more prone to believing that accelerated conventional and newly-emerging renewables, and greatly improved efficiency, along with social change, can succeed. Both routes have risks, as well as possible strategic benefits and synergies, as I have explored in my last few posts. It may come down to faith in technology and change. CCS has been promoted as a key way ahead but has not so far delivered. Renewables have, and strikingly so, with costs falling. So why not give them a chance?

The debate continues and indeed expands, with, as Carbon Brief reports, a new study in PNAS claiming that there is a range of non-BECCS natural carbon capture options (including reafforestation, biochar production, “no till” soil management) that can possibly avoid the need for BECCS. If true, that changes everything. The net CO₂ balance calculations are, however, complex and depend on what type of biomass is used and where it is grown. So there is still some uncertainty. Nevertheless, depending on the sources used and their impacts, it may be that BECCS may not be the best option in many cases and may not lead to much in the way of negative carbon. If that proves to be the case, then we should maybe forget about BECCS, although some might say “not entirely”: we might need a bit, and other carbon capture options – belt and braces – in case renewables can’t accelerate fast enough.